Pulmonary function is known to be related inversely to incidence of coronary heart disease, congestive heart failure, chronic obstructive lung disease, lung cancer, and death from all causes. Reasons for some of these associations are poorly understood. Relationships between cardiovascular disease risk factors and pulmonary function were examined in 5,115 18- to 30-year-old black and white male and female participants in the study of Coronary Artery Risk Development in Young Adults (CARDIA). Forced expiratory volume in 1 s adjusted for height (FEV1/Ht2) was significantly lower in smokers than nonsmokers and in persons who reported shortness of breath; FEV1/Ht2 was correlated positively with a history of strenuous physical activity, duration of exercise on the treadmill, and high-density lipoprotein cholesterol. It was associated negatively with skinfold thicknesses, serum triglycerides, fasting serum insulin, and the Cook Medley scale of hostility. The association between pulmonary function and heart disease risk may reflect associations with physical fitness, vigor, fatness, and lipid profiles, as well as with cigarette smoking.